Further studies examining genetic and environmental contributions to the expression of hand preference were performed in chimpanzees. Furthermore, the possible consequences and neuroanatomical correlates of hand preference were examined in the chimpanzees. The findings from this year indicate a) individual variation in hand preference can be explained by variation in prenatal hormones b) birth order has a significant effect on hand preference and c) variation in prenatal hormone exposure has a significant impact on maternal outcome and neonatal fatalities. Additionally, the chimpanzees exhibit neuroanatomical asymmetries that are human-like in pattern and are related to variation in the size of the corpus callosum. Taken together, the results of this study further our understanding of the role of laterality as a marker of reduced fitness in humans. FUNDING NIH / NS-29574 $65,000 12/01/98 - 11/31/03 PUBLICATIONS Hopkins, W. D. The evolutionary and genetic (possibly?) basis of hand preference in humans What can the great apes tell us. Current Psychology of Cognition 3:234-238, 1998. Hopkins, W.D. Heritability of hand preference in chimpanzees Evidence from a interspecies partial cross-fostering study, Journal of Comparative Psychology (In press). Hopkins, W.D. Statistical issues in the assessment and interpretation of hand preference data in nonhuman primates, International Journal of Primatology (In press). Hopkins, W.D. Chimpanzees hand preferences Task specific or true handedness? Journal of Comparative Psychology (In press). Leavens, D.A. and Hopkins, W.D. Gestural communication in chimpanzees Implication for theories regarding social cognition. Journal of Comparative Psychology (In press). Parr, L.A., Hopkins, W.D. and deWaal, F.B.M. The perception of facial expression by chimpanzees. Evolution of Communication (In press). P51RR00165-38 1/1/1998 - 12/31/1998 Yerkes Regional Primate Research Center